Gene therapy represents the technology by which human genes are transferred to target cells thus modifying the genetic composition of the targets. In regards to the lung, two strategies are being employed to utilize this technology to treat human lung disorders. First, adenovirus-based replication deficient recombinant vectors are being used to directly transfer genes to the respiratory epithelium and liver in vivo. This has been accomplished with the human genes representing the two major lethal hereditary disorders in the United States and Europe, cystic fibrosis and alpha1-antitrypsin deficiency. Although safety aspects of this strategy for the therapy of these disorders will have to be demonstrated, the results are encouraging breakthroughs in the design of approaches to the ultimate "cure" of these disorders. Ongoing studies are directed to bringing this technology to the bedside, for direct in vivo transfer of these genes to humans as therapy for lung disease.